BTK抑制剂治疗进展的CLL患者中BTK和PLCG2突变的患病率:一项荟萃分析

IF 10.1 1区 医学 Q1 HEMATOLOGY
Stefano Molica, David Allsup, Diana Giannarelli
{"title":"BTK抑制剂治疗进展的CLL患者中BTK和PLCG2突变的患病率:一项荟萃分析","authors":"Stefano Molica, David Allsup, Diana Giannarelli","doi":"10.1002/ajh.27544","DOIUrl":null,"url":null,"abstract":"<p>Bruton's tyrosine kinase inhibitors (BTKis) have revolutionized the treatment of chronic lymphocytic leukemia (CLL), with significantly improved outcomes for both treatment-naïve (TN) and relapsed/refractory (R/R) patients. BTKis bind irreversibly to the cysteine 481 (<i>C481</i>) residue of the BTK molecule inhibiting B-cell receptor (BCR)-mediated intracellular signals crucial for CLL-cell survival [<span>1</span>]. Despite its efficacy, long-term BTKi therapy often leads to therapy resistance with subsequent disease progression (DP) [<span>2</span>]. Resistance mechanisms predominantly relate to mutations in <i>BTK</i> gene, particularly the mutation at <i>C481S</i>, which disrupts covalent BTKi binding. Additionally, mutations in phospholipase Cγ2 (<i>PLCG2</i>), which encodes for a downstream effector of BCR signaling, are emerging as significant additional contributors to resistance [<span>3</span>].</p>\n<p>To comprehensively assess the prevalence and significance of these resistance mechanisms, we conducted a systematic review and meta-analysis to quantify the prevalence of <i>BTK</i> and <i>PLCG2</i> mutations in CLL patients who experience DP while treated with BTKis. We performed a comprehensive search of the PubMed database and manually reviewed abstracts from major hematology conferences (American Society Hematology [ASH] and European Hematology Association [EHA]) to identify relevant studies. The analysis adhered to Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines to ensure methodological rigor and transparency [<span>4</span>].</p>\n<p>Studies were included if they reported upon CLL patients treated with covalent BTKis and reported assessments for <i>BTK</i> and/or <i>PLCG2</i> mutations at DP. Two reviewers (SM and DG) independently performed data extraction, with discrepancies resolved by consensus. The primary outcome was the pooled prevalence of <i>BTK</i> and <i>PLCG2</i> mutations amongst patients with DP while treated with BTKis. A separate analysis compared patients treated with first-generation BTKi (ibrutinib) versus second-generation BTKis (acalabrutinib, zanubrutinib). Cross study heterogeneity was assessed using the chi-squared (<i>χ</i><sup>2</sup>) <i>Q</i> test and the <i>I</i><sup>2</sup> statistic, with an <i>I</i><sup>2</sup> value greater than 50% indicating substantial heterogeneity.</p>\n<p>Seventeen studies with 724 patients provided data on <i>BTK</i> somatic mutations [<span>2, 3</span>] (Figure S1; Table S1; Supporting Information: References [1–11]). These studies included six post hoc analyses of Phase 3 clinical trials (ALPINE, ELEVATE R/R, RESONATE, RESONATE-2, ILLUMINATE, FLAIR), five Phase 2 trials (PCYC-1122, RESONATE-17, NCT02337829, NCT01500733, NCT03740529 [BRUIN]), and three retrospective multicenter analyses (French Innovative Leukemia Organization [FILO], European Research Initiative on CLL [ERIC], Hungarian Ibrutinib Resistance Analysis Initiative). Additionally, three retrospective monocentric studies from the MD Anderson Cancer Center (MDACC), Peter MacCallum Cancer Centre, and The Ohio State University (OSU) Comprehensive Cancer Center were included [<span>2, 3</span>] (Supporting Information: References [1–11]). The majority of patients (86.4%) received ibrutinib-based therapies (ibrutinib monotherapy, 78%; ibrutinib combined with rituximab [IR], 8.4%), while a smaller subset (13.5%) received second-generation BTKis (acalabrutinib, 8.4%; zanubrutinib, 5.1%).</p>\n<p>Overall, 7.8% of patients discontinued BTKi therapy due to adverse events (AEs) or other reasons. Of those who discontinued due to DP (<i>n</i> = 667), 86.3% had R/R CLL, and 13.6% had TN CLL. The meta-analysis demonstrated that, amongst patients with progressive CLL, pooled prevalence of <i>BTK</i> mutations was 52% (95% CI: 39%–64%), but with substantial heterogeneity across studies (<i>Q</i> = 161.54, <i>p</i> &lt; 0.001, <i>I</i><sup>2</sup> = 91%) (Figure 1A).</p>\n<figure><picture>\n<source media=\"(min-width: 1650px)\" srcset=\"/cms/asset/ede14e39-0e15-4b09-af64-cb3f700f5268/ajh27544-fig-0001-m.jpg\"/><img alt=\"Details are in the caption following the image\" data-lg-src=\"/cms/asset/ede14e39-0e15-4b09-af64-cb3f700f5268/ajh27544-fig-0001-m.jpg\" loading=\"lazy\" src=\"/cms/asset/a8edbccc-e8bd-4986-8278-a644397e8d4e/ajh27544-fig-0001-m.png\" title=\"Details are in the caption following the image\"/></picture><figcaption>\n<div><strong>FIGURE 1<span style=\"font-weight:normal\"></span></strong><div>Open in figure viewer<i aria-hidden=\"true\"></i><span>PowerPoint</span></div>\n</div>\n<div>Meta-analysis on the prevalence of Bruton tyrosine kinase (<i>BTK</i>) (A) and phospholipase Cγ2 (<i>PLCG2</i>) (B) somatic mutations amongst patients with disease progression (DP) while treated with BTK inhibitor therapy.</div>\n</figcaption>\n</figure>\n<p>Fourteen studies, which encompassed 620 patients, were analyzed for <i>PLCG2</i> mutations [<span>2, 3</span>] (Figure S2; Table S1) (Supporting Information: References [1–5, 9–11]). These cohorts were the same as those analyzed for <i>BTK</i> mutations, except for the noninclusion of the patients from the MDACC, Peter MacCallum Cancer Centre, and the Hungarian Ibrutinib Resistance Analysis Initiative, which did not provide data on <i>PLCG2</i> mutations. Most patients in the <i>PLCG2</i> cohort were treated with ibrutinib-based therapies (ibrutinib-monotherapy, 80.3%; IR, 9.8%), while a smaller proportion (13.7%) received second-generation BTKis (acalabrutinib, 9.8%; zanubrutinib, 3.8%). Discontinuation of BTKi therapy due to AEs or other reasons was observed in 9.2% of patients. Amongst patients with progressive CLL (<i>n</i> = 563), 86% had R/R CLL, and 14% had TN CLL. The pooled prevalence of <i>PLCG2</i> mutations was 11% (95% CI: 7%–17%), with notable heterogeneity across studies (<i>Q</i> = 40.77, <i>p</i> &lt; 0.001, <i>I</i><sup>2</sup> = 73%) (Figure 1B).</p>\n<p>We further explored whether the prevalence of <i>BTK</i> or <i>PLCG2</i> mutations differed between patients treated with the first-generation BTKi ibrutinib and those treated with the second-generation inhibitors acalabrutinib or zanubrutinib. The prevalence of <i>BTK</i> mutations was 56% (95% CI: 38%–74%) amongst ibrutinib-treated patients and 51% (95% CI: 26%–77%) amongst those treated with acalabrutinib or zanubrutinib (Figure S3). <i>PLCG2</i> mutations were detected in 13% (95% CI: 6%–23%) of ibrutinib-treated patients, compared with 9% (95% CI: 0%–25%) in patients exposed to acalabrutinib or zanubrutinib (Figure S4).</p>\n<p>Finally, we investigated whether pre-existing <i>TP53</i> mutations (median 49.5%; range 22.9%–100%) or the duration of BTKi therapy (median 40.5 months; range 27.7–78 months) correlated with the development of <i>BTK</i> and <i>PLCG2</i> mutations.</p>\n<p>A positive correlation was found between the presence of <i>PLCG2</i> mutations and the <i>TP53</i> mutational burden (<i>r</i><sup>2</sup> = 0.872, <i>p</i> = 0.001), as well as the duration of BTKi therapy (<i>r</i><sup>2</sup> = 0.539, <i>p</i> = 0.02) (Figures S5 and S6). However, no significant correlation was observed between these factors and the presence of <i>BTK</i> mutations.</p>\n<p>Our meta-analysis demonstrates that resistance to BTKis in CLL is multifaceted, with <i>BTK</i> mutations prevalent in over half of patients who experience DP. While <i>PLCG2</i> mutations are less common, their association with a high <i>TP53</i> mutation burden and prolonged BTKi exposure underscores their emergent role in secondary resistance mechanisms. These results may suggest that fixed-duration therapies could mitigate these resistance pathways, with potential improvement in long-term outcomes for patients [<span>5, 6</span>].</p>\n<p>Given the limited representation of TN CLL patients in our dataset, these findings primarily pertain to patients with R/R CLL. Notably, most R/R patients were likely exposed to prior chemotherapy. In our aggregate analysis, however, we could not differentiate between R/R patients with and without prior chemotherapy exposure. Therefore, the specific contribution of prior chemotherapy to BTKi resistance mediated by <i>BTK</i> or <i>PLCG2</i> mutations could not be assessed in detail.</p>\n<p>Much of our knowledge in relation to the prevalence of <i>BTK</i> or <i>PLCG2</i> mutations is derived from studies of ibrutinib-treated patients [<span>2, 3</span>] (Supporting Information: References [1–11]). A recent post hoc analysis of the ELEVATE-R/R trial, which compared acalabrutinib with ibrutinib in R/R high-risk CLL patients, revealed that the rate of emergent <i>BTK</i> mutations at relapse was significantly lower in those treated with ibrutinib as compared to acalabrutinib (37% vs. 69%) (Supporting Information: Reference [2]). However, due to the limited sample size associated with this analysis, the clinical significance of these findings remains uncertain. Additionally, the presence of higher risk genomic features amongst patients in the ELEVATE-RR trial, which contributes to genetic instability, limits the generalizability of these results (Supporting Information: Reference [2]). In our meta-analysis of trials involving ibrutinib and second-generation BTKis, we observed similar rates of <i>BTK</i> and <i>PLCG2</i> mutations amongst patients with progressive disease, regardless of the specific BTKi used.</p>\n<p>An important consideration in the transition from ibrutinib to second-generation BTKis is the emergence of additional <i>BTK</i> mutations that mediate resistance. In a post hoc analysis of the ELEVATE-R/R trial, <i>T474I</i> gatekeeper mutations were observed in 29% of patients exhibiting resistance to acalabrutinib (Supporting Information: Reference [2]). In a separate study examining patients treated with zanubrutinib, <i>L528W</i> mutations, known to impair kinase function, were detected at rates comparable to those of the <i>C481S</i> mutation (Supporting Information: Reference [3]). Our analysis confirms that the canonical C481S mutation remains the predominant mutation, accounting for approximately 60%–100% of <i>BTK</i> mutations in patients treated with ibrutinib or second-generation BTK inhibitors (Table S2).</p>\n<p>Finally, it is important to acknowledge the limitations of our current meta-analysis. While our current study points to somatic genetic mutations as the primary drivers of resistance, one-third of the patients in our analysis lacked either detectable <i>BTK</i> or <i>PLCG2</i> mutations. In these patients, resistance to BTKis may develop through nongenetic adaptive mechanisms that activate compensatory pro-survival pathways. Specifically, the activation of PI3K/AKT/ mTOR, NF-κB, and MAPK pathways, along with the upregulation of BCL2, MYC, and XPO1 or downregulation of PTEN, may enable B cell survival even in the presence of BTK inhibition [<span>7</span>]. Additionally, resistance may be further supported by microenvironmental factors, including chemokine and integrin signaling via upregulation of CXCR4 and VLA4 [<span>7</span>]. Such mechanisms may also be pathogenic mediators of BTKi therapy resistance, concepts, which challenge the predominant focus on genetic factors in this field of study.</p>\n<p>Other limitations of this study include the inconsistent reporting of variant allele frequencies (VAFs), the reliance on peripheral blood samples that may not capture clonal evolution in lymph nodes and the lack of longitudinal data mapping mutation dynamics over time [<span>8</span>].</p>\n<p>In summary, this meta-analysis provides a comprehensive insight into the prevalence of <i>BTK</i> and <i>PLCG2</i> somatic mutations in CLL, which has lost sensitivity to BTKi therapy. Our report may lead to a further appreciation of genetic mechanisms of resistance to BTKis in CLL treatment. Ultimately, the heterogeneity of resistance mechanisms necessitate further research also into nongenetic factors driving DP.</p>","PeriodicalId":7724,"journal":{"name":"American Journal of Hematology","volume":"37 1","pages":""},"PeriodicalIF":10.1000,"publicationDate":"2024-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Prevalence of BTK and PLCG2 Mutations in CLL Patients With Disease Progression on BTK Inhibitor Therapy: A Meta‐Analysis\",\"authors\":\"Stefano Molica, David Allsup, Diana Giannarelli\",\"doi\":\"10.1002/ajh.27544\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p>Bruton's tyrosine kinase inhibitors (BTKis) have revolutionized the treatment of chronic lymphocytic leukemia (CLL), with significantly improved outcomes for both treatment-naïve (TN) and relapsed/refractory (R/R) patients. BTKis bind irreversibly to the cysteine 481 (<i>C481</i>) residue of the BTK molecule inhibiting B-cell receptor (BCR)-mediated intracellular signals crucial for CLL-cell survival [<span>1</span>]. Despite its efficacy, long-term BTKi therapy often leads to therapy resistance with subsequent disease progression (DP) [<span>2</span>]. Resistance mechanisms predominantly relate to mutations in <i>BTK</i> gene, particularly the mutation at <i>C481S</i>, which disrupts covalent BTKi binding. Additionally, mutations in phospholipase Cγ2 (<i>PLCG2</i>), which encodes for a downstream effector of BCR signaling, are emerging as significant additional contributors to resistance [<span>3</span>].</p>\\n<p>To comprehensively assess the prevalence and significance of these resistance mechanisms, we conducted a systematic review and meta-analysis to quantify the prevalence of <i>BTK</i> and <i>PLCG2</i> mutations in CLL patients who experience DP while treated with BTKis. We performed a comprehensive search of the PubMed database and manually reviewed abstracts from major hematology conferences (American Society Hematology [ASH] and European Hematology Association [EHA]) to identify relevant studies. The analysis adhered to Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines to ensure methodological rigor and transparency [<span>4</span>].</p>\\n<p>Studies were included if they reported upon CLL patients treated with covalent BTKis and reported assessments for <i>BTK</i> and/or <i>PLCG2</i> mutations at DP. Two reviewers (SM and DG) independently performed data extraction, with discrepancies resolved by consensus. The primary outcome was the pooled prevalence of <i>BTK</i> and <i>PLCG2</i> mutations amongst patients with DP while treated with BTKis. A separate analysis compared patients treated with first-generation BTKi (ibrutinib) versus second-generation BTKis (acalabrutinib, zanubrutinib). Cross study heterogeneity was assessed using the chi-squared (<i>χ</i><sup>2</sup>) <i>Q</i> test and the <i>I</i><sup>2</sup> statistic, with an <i>I</i><sup>2</sup> value greater than 50% indicating substantial heterogeneity.</p>\\n<p>Seventeen studies with 724 patients provided data on <i>BTK</i> somatic mutations [<span>2, 3</span>] (Figure S1; Table S1; Supporting Information: References [1–11]). These studies included six post hoc analyses of Phase 3 clinical trials (ALPINE, ELEVATE R/R, RESONATE, RESONATE-2, ILLUMINATE, FLAIR), five Phase 2 trials (PCYC-1122, RESONATE-17, NCT02337829, NCT01500733, NCT03740529 [BRUIN]), and three retrospective multicenter analyses (French Innovative Leukemia Organization [FILO], European Research Initiative on CLL [ERIC], Hungarian Ibrutinib Resistance Analysis Initiative). Additionally, three retrospective monocentric studies from the MD Anderson Cancer Center (MDACC), Peter MacCallum Cancer Centre, and The Ohio State University (OSU) Comprehensive Cancer Center were included [<span>2, 3</span>] (Supporting Information: References [1–11]). The majority of patients (86.4%) received ibrutinib-based therapies (ibrutinib monotherapy, 78%; ibrutinib combined with rituximab [IR], 8.4%), while a smaller subset (13.5%) received second-generation BTKis (acalabrutinib, 8.4%; zanubrutinib, 5.1%).</p>\\n<p>Overall, 7.8% of patients discontinued BTKi therapy due to adverse events (AEs) or other reasons. Of those who discontinued due to DP (<i>n</i> = 667), 86.3% had R/R CLL, and 13.6% had TN CLL. The meta-analysis demonstrated that, amongst patients with progressive CLL, pooled prevalence of <i>BTK</i> mutations was 52% (95% CI: 39%–64%), but with substantial heterogeneity across studies (<i>Q</i> = 161.54, <i>p</i> &lt; 0.001, <i>I</i><sup>2</sup> = 91%) (Figure 1A).</p>\\n<figure><picture>\\n<source media=\\\"(min-width: 1650px)\\\" srcset=\\\"/cms/asset/ede14e39-0e15-4b09-af64-cb3f700f5268/ajh27544-fig-0001-m.jpg\\\"/><img alt=\\\"Details are in the caption following the image\\\" data-lg-src=\\\"/cms/asset/ede14e39-0e15-4b09-af64-cb3f700f5268/ajh27544-fig-0001-m.jpg\\\" loading=\\\"lazy\\\" src=\\\"/cms/asset/a8edbccc-e8bd-4986-8278-a644397e8d4e/ajh27544-fig-0001-m.png\\\" title=\\\"Details are in the caption following the image\\\"/></picture><figcaption>\\n<div><strong>FIGURE 1<span style=\\\"font-weight:normal\\\"></span></strong><div>Open in figure viewer<i aria-hidden=\\\"true\\\"></i><span>PowerPoint</span></div>\\n</div>\\n<div>Meta-analysis on the prevalence of Bruton tyrosine kinase (<i>BTK</i>) (A) and phospholipase Cγ2 (<i>PLCG2</i>) (B) somatic mutations amongst patients with disease progression (DP) while treated with BTK inhibitor therapy.</div>\\n</figcaption>\\n</figure>\\n<p>Fourteen studies, which encompassed 620 patients, were analyzed for <i>PLCG2</i> mutations [<span>2, 3</span>] (Figure S2; Table S1) (Supporting Information: References [1–5, 9–11]). These cohorts were the same as those analyzed for <i>BTK</i> mutations, except for the noninclusion of the patients from the MDACC, Peter MacCallum Cancer Centre, and the Hungarian Ibrutinib Resistance Analysis Initiative, which did not provide data on <i>PLCG2</i> mutations. Most patients in the <i>PLCG2</i> cohort were treated with ibrutinib-based therapies (ibrutinib-monotherapy, 80.3%; IR, 9.8%), while a smaller proportion (13.7%) received second-generation BTKis (acalabrutinib, 9.8%; zanubrutinib, 3.8%). Discontinuation of BTKi therapy due to AEs or other reasons was observed in 9.2% of patients. Amongst patients with progressive CLL (<i>n</i> = 563), 86% had R/R CLL, and 14% had TN CLL. The pooled prevalence of <i>PLCG2</i> mutations was 11% (95% CI: 7%–17%), with notable heterogeneity across studies (<i>Q</i> = 40.77, <i>p</i> &lt; 0.001, <i>I</i><sup>2</sup> = 73%) (Figure 1B).</p>\\n<p>We further explored whether the prevalence of <i>BTK</i> or <i>PLCG2</i> mutations differed between patients treated with the first-generation BTKi ibrutinib and those treated with the second-generation inhibitors acalabrutinib or zanubrutinib. The prevalence of <i>BTK</i> mutations was 56% (95% CI: 38%–74%) amongst ibrutinib-treated patients and 51% (95% CI: 26%–77%) amongst those treated with acalabrutinib or zanubrutinib (Figure S3). <i>PLCG2</i> mutations were detected in 13% (95% CI: 6%–23%) of ibrutinib-treated patients, compared with 9% (95% CI: 0%–25%) in patients exposed to acalabrutinib or zanubrutinib (Figure S4).</p>\\n<p>Finally, we investigated whether pre-existing <i>TP53</i> mutations (median 49.5%; range 22.9%–100%) or the duration of BTKi therapy (median 40.5 months; range 27.7–78 months) correlated with the development of <i>BTK</i> and <i>PLCG2</i> mutations.</p>\\n<p>A positive correlation was found between the presence of <i>PLCG2</i> mutations and the <i>TP53</i> mutational burden (<i>r</i><sup>2</sup> = 0.872, <i>p</i> = 0.001), as well as the duration of BTKi therapy (<i>r</i><sup>2</sup> = 0.539, <i>p</i> = 0.02) (Figures S5 and S6). However, no significant correlation was observed between these factors and the presence of <i>BTK</i> mutations.</p>\\n<p>Our meta-analysis demonstrates that resistance to BTKis in CLL is multifaceted, with <i>BTK</i> mutations prevalent in over half of patients who experience DP. While <i>PLCG2</i> mutations are less common, their association with a high <i>TP53</i> mutation burden and prolonged BTKi exposure underscores their emergent role in secondary resistance mechanisms. These results may suggest that fixed-duration therapies could mitigate these resistance pathways, with potential improvement in long-term outcomes for patients [<span>5, 6</span>].</p>\\n<p>Given the limited representation of TN CLL patients in our dataset, these findings primarily pertain to patients with R/R CLL. Notably, most R/R patients were likely exposed to prior chemotherapy. In our aggregate analysis, however, we could not differentiate between R/R patients with and without prior chemotherapy exposure. Therefore, the specific contribution of prior chemotherapy to BTKi resistance mediated by <i>BTK</i> or <i>PLCG2</i> mutations could not be assessed in detail.</p>\\n<p>Much of our knowledge in relation to the prevalence of <i>BTK</i> or <i>PLCG2</i> mutations is derived from studies of ibrutinib-treated patients [<span>2, 3</span>] (Supporting Information: References [1–11]). A recent post hoc analysis of the ELEVATE-R/R trial, which compared acalabrutinib with ibrutinib in R/R high-risk CLL patients, revealed that the rate of emergent <i>BTK</i> mutations at relapse was significantly lower in those treated with ibrutinib as compared to acalabrutinib (37% vs. 69%) (Supporting Information: Reference [2]). However, due to the limited sample size associated with this analysis, the clinical significance of these findings remains uncertain. Additionally, the presence of higher risk genomic features amongst patients in the ELEVATE-RR trial, which contributes to genetic instability, limits the generalizability of these results (Supporting Information: Reference [2]). In our meta-analysis of trials involving ibrutinib and second-generation BTKis, we observed similar rates of <i>BTK</i> and <i>PLCG2</i> mutations amongst patients with progressive disease, regardless of the specific BTKi used.</p>\\n<p>An important consideration in the transition from ibrutinib to second-generation BTKis is the emergence of additional <i>BTK</i> mutations that mediate resistance. In a post hoc analysis of the ELEVATE-R/R trial, <i>T474I</i> gatekeeper mutations were observed in 29% of patients exhibiting resistance to acalabrutinib (Supporting Information: Reference [2]). In a separate study examining patients treated with zanubrutinib, <i>L528W</i> mutations, known to impair kinase function, were detected at rates comparable to those of the <i>C481S</i> mutation (Supporting Information: Reference [3]). Our analysis confirms that the canonical C481S mutation remains the predominant mutation, accounting for approximately 60%–100% of <i>BTK</i> mutations in patients treated with ibrutinib or second-generation BTK inhibitors (Table S2).</p>\\n<p>Finally, it is important to acknowledge the limitations of our current meta-analysis. While our current study points to somatic genetic mutations as the primary drivers of resistance, one-third of the patients in our analysis lacked either detectable <i>BTK</i> or <i>PLCG2</i> mutations. In these patients, resistance to BTKis may develop through nongenetic adaptive mechanisms that activate compensatory pro-survival pathways. Specifically, the activation of PI3K/AKT/ mTOR, NF-κB, and MAPK pathways, along with the upregulation of BCL2, MYC, and XPO1 or downregulation of PTEN, may enable B cell survival even in the presence of BTK inhibition [<span>7</span>]. Additionally, resistance may be further supported by microenvironmental factors, including chemokine and integrin signaling via upregulation of CXCR4 and VLA4 [<span>7</span>]. Such mechanisms may also be pathogenic mediators of BTKi therapy resistance, concepts, which challenge the predominant focus on genetic factors in this field of study.</p>\\n<p>Other limitations of this study include the inconsistent reporting of variant allele frequencies (VAFs), the reliance on peripheral blood samples that may not capture clonal evolution in lymph nodes and the lack of longitudinal data mapping mutation dynamics over time [<span>8</span>].</p>\\n<p>In summary, this meta-analysis provides a comprehensive insight into the prevalence of <i>BTK</i> and <i>PLCG2</i> somatic mutations in CLL, which has lost sensitivity to BTKi therapy. Our report may lead to a further appreciation of genetic mechanisms of resistance to BTKis in CLL treatment. Ultimately, the heterogeneity of resistance mechanisms necessitate further research also into nongenetic factors driving DP.</p>\",\"PeriodicalId\":7724,\"journal\":{\"name\":\"American Journal of Hematology\",\"volume\":\"37 1\",\"pages\":\"\"},\"PeriodicalIF\":10.1000,\"publicationDate\":\"2024-12-07\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"American Journal of Hematology\",\"FirstCategoryId\":\"3\",\"ListUrlMain\":\"https://doi.org/10.1002/ajh.27544\",\"RegionNum\":1,\"RegionCategory\":\"医学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"HEMATOLOGY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"American Journal of Hematology","FirstCategoryId":"3","ListUrlMain":"https://doi.org/10.1002/ajh.27544","RegionNum":1,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"HEMATOLOGY","Score":null,"Total":0}
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摘要

Bruton的酪氨酸激酶抑制剂(BTKis)彻底改变了慢性淋巴细胞白血病(CLL)的治疗,显著改善了treatment-naïve (TN)和复发/难治性(R/R)患者的预后。BTKis不可逆地结合BTK分子的半胱氨酸481 (C481)残基,抑制b细胞受体(BCR)介导的细胞内信号,这对cll细胞存活至关重要。尽管其疗效显著,但长期BTKi治疗经常导致治疗耐药,并伴有随后的疾病进展(DP)[2]。耐药机制主要与BTK基因突变有关,特别是C481S突变,该突变破坏了共价BTKi结合。此外,编码BCR信号下游效应的磷脂酶c - γ - 2 (PLCG2)的突变正在成为[3]抗性的重要附加因素。为了全面评估这些耐药机制的患病率和重要性,我们进行了一项系统回顾和荟萃分析,以量化BTK和PLCG2突变在接受BTKis治疗的DP CLL患者中的患病率。我们对PubMed数据库进行了全面的搜索,并手动审查了主要血液学会议(美国血液学学会[ASH]和欧洲血液学协会[EHA])的摘要,以确定相关研究。该分析遵循了系统评价和荟萃分析(PRISMA)指南的首选报告项目,以确保方法的严谨性和透明度。如果研究报告了CLL患者接受共价BTKis治疗,并报告了DP时BTK和/或PLCG2突变的评估,则纳入研究。两名审稿人(SM和DG)独立进行数据提取,差异通过共识解决。主要结果是在接受BTKis治疗的DP患者中BTK和PLCG2突变的总流行率。另一项分析比较了第一代BTKi(伊鲁替尼)和第二代BTKi(阿卡拉布替尼、扎努布替尼)治疗的患者。采用χ2检验和I2统计量评估交叉研究异质性,I2值大于50%表明存在显著异质性。17项涉及724例患者的研究提供了BTK体细胞突变的数据[2,3](图S1;表S1;文献资料[1-11])。这些研究包括6项3期临床试验的事后分析(ALPINE、ELEVATE R/R、resonance、resonance -2、ILLUMINATE、FLAIR), 5项2期试验(PCYC-1122、resonance -17、NCT02337829、NCT01500733、NCT03740529 [BRUIN]),以及3项回顾性多中心分析(法国创新白血病组织[FILO]、欧洲CLL研究倡议[ERIC]、匈牙利伊鲁替尼耐药性分析倡议)。此外,我们还纳入了MD安德森癌症中心(MDACC)、Peter MacCallum癌症中心和俄亥俄州立大学(OSU)综合癌症中心的三项回顾性单中心研究[2,3](辅助信息:参考文献[1-11])。大多数患者(86.4%)接受了以伊鲁替尼为基础的治疗(伊鲁替尼单药治疗,78%;伊鲁替尼联合利妥昔单抗[IR], 8.4%),而较小的子集(13.5%)接受第二代BTKis(阿卡拉布替尼,8.4%;zanubrutinib, 5.1%)。总体而言,7.8%的患者因不良事件(ae)或其他原因停止BTKi治疗。在因DP停药的患者中(n = 667), 86.3%为R/R CLL, 13.6%为TN CLL。荟萃分析显示,在进行性CLL患者中,BTK突变的总患病率为52% (95% CI: 39%-64%),但各研究之间存在很大的异质性(Q = 161.54, p &lt; 0.001, I2 = 91%)(图1A)。在接受BTK抑制剂治疗的疾病进展(DP)患者中,布鲁顿酪氨酸激酶(BTK) (A)和磷脂酶Cγ2 (PLCG2) (B)体细胞突变患病率的meta分析。对包含620例患者的14项研究进行了PLCG2突变分析[2,3](图S2;表S1)(支持信息:参考文献[1 - 5,9 - 11])。除了MDACC、Peter MacCallum癌症中心和匈牙利伊鲁替尼耐药分析计划(Ibrutinib Resistance Analysis Initiative)的患者没有提供PLCG2突变的数据外,这些队列与BTK突变分析的队列相同。PLCG2队列中的大多数患者接受以伊鲁替尼为基础的治疗(伊鲁替尼单药治疗,80.3%;IR, 9.8%),而较小比例(13.7%)接受第二代BTKis (acalabrutinib, 9.8%;zanubrutinib, 3.8%)。9.2%的患者因不良事件或其他原因停止BTKi治疗。在进展性CLL患者中(n = 563), 86%为R/R CLL, 14%为TN CLL。PLCG2突变的总患病率为11% (95% CI: 7%-17%),各研究之间存在显著的异质性(Q = 40.77, p &lt; 0.001, I2 = 73%)(图1B)。 我们进一步探讨了使用第一代BTKi ibrutinib治疗的患者与使用第二代抑制剂acalabrutinib或zanubrutinib治疗的患者之间BTK或PLCG2突变的患病率是否存在差异。在伊鲁替尼治疗的患者中,BTK突变的发生率为56% (95% CI: 38%-74%),而在阿卡拉布替尼或扎鲁替尼治疗的患者中,BTK突变的发生率为51% (95% CI: 26%-77%)(图S3)。在伊鲁替尼治疗的患者中,有13% (95% CI: 6%-23%)检测到PLCG2突变,而在阿卡拉布替尼或扎鲁替尼暴露的患者中,这一比例为9% (95% CI: 0%-25%)(图S4)。最后,我们调查了先前存在的TP53突变(中位数49.5%;范围22.9%-100%)或BTKi治疗的持续时间(中位40.5个月;范围27.7-78个月)与BTK和PLCG2突变的发生相关。PLCG2突变的存在与TP53突变负荷呈正相关(r2 = 0.872, p = 0.001),与BTKi治疗时间呈正相关(r2 = 0.539, p = 0.02)(图S5和S6)。然而,这些因素与BTK突变之间没有明显的相关性。我们的荟萃分析表明,CLL患者对BTKis的耐药性是多方面的,超过一半的DP患者普遍存在BTK突变。虽然PLCG2突变不太常见,但它们与高TP53突变负担和长时间BTKi暴露的关联强调了它们在继发性耐药机制中的新作用。这些结果可能表明,固定时间的治疗可以减轻这些耐药途径,并可能改善患者的长期预后[5,6]。鉴于我们的数据集中TN CLL患者的代表性有限,这些发现主要适用于R/R CLL患者。值得注意的是,大多数R/R患者可能曾接受过化疗。然而,在我们的综合分析中,我们无法区分是否接受过化疗的R/R患者。因此,无法详细评估先前化疗对BTK或PLCG2突变介导的BTKi耐药的具体贡献。我们关于BTK或PLCG2突变患病率的大部分知识来自于对伊鲁替尼治疗患者的研究[2,3](支持信息:参考文献[1-11])。最近的一项对ELEVATE-R/R试验的事后分析,该试验比较了阿卡拉布替尼和伊鲁替尼在R/R高风险CLL患者中的作用,结果显示,与阿卡拉布替尼相比,伊鲁替尼治疗的复发时出现BTK突变率显着降低(37%对69%)(支持信息:参考文献[2])。然而,由于与该分析相关的样本量有限,这些发现的临床意义仍不确定。此外,在ELEVATE-RR试验患者中存在高风险基因组特征,这有助于遗传不稳定性,限制了这些结果的普遍性(支持信息:参考文献[2])。在我们对涉及依鲁替尼和第二代BTKi的试验的荟萃分析中,我们观察到,无论使用何种特定的BTKi,进展性疾病患者的BTK和PLCG2突变率相似。从依鲁替尼过渡到第二代BTKis的一个重要考虑因素是出现了介导耐药的额外BTK突变。在一项对elevation -R/R试验的事后分析中,在29%对阿卡拉布替尼耐药的患者中观察到T474I守门人突变(支持信息:参考文献[2])。在另一项对接受扎鲁替尼治疗的患者进行的研究中,已知会损害激酶功能的L528W突变的检测率与C481S突变的检测率相当(支持信息:参考文献[3])。我们的分析证实,典型的C481S突变仍然是主要突变,约占伊鲁替尼或第二代BTK抑制剂治疗患者BTK突变的60%-100%(表S2)。最后,承认我们当前meta分析的局限性是很重要的。虽然我们目前的研究指出体细胞基因突变是耐药的主要驱动因素,但在我们的分析中,三分之一的患者缺乏可检测的BTK或PLCG2突变。在这些患者中,对BTKis的耐药性可能通过激活代偿性促生存途径的非遗传适应性机制发展。具体来说,PI3K/AKT/ mTOR、NF-κB和MAPK通路的激活,以及BCL2、MYC和XPO1的上调或PTEN的下调,即使在BTK抑制[7]的情况下,也可能使B细胞存活。此外,耐药可能进一步受到微环境因素的支持,包括趋化因子和整合素信号,通过上调CXCR4和vla4[7]。这些机制也可能是BTKi治疗耐药的致病介质,这一概念挑战了该研究领域主要关注遗传因素的研究。 本研究的其他局限性包括变异等位基因频率(VAFs)的报告不一致,对外周血样本的依赖可能无法捕获淋巴结中的克隆进化,以及缺乏随时间变化的突变动态的纵向数据。总之,本荟萃分析提供了对BTK和PLCG2体细胞突变在对BTKi治疗失去敏感性的CLL中的患病率的全面见解。我们的报告可能会导致对CLL治疗中BTKis耐药的遗传机制的进一步认识。最终,抗性机制的异质性需要进一步研究驱动DP的非遗传因素。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Prevalence of BTK and PLCG2 Mutations in CLL Patients With Disease Progression on BTK Inhibitor Therapy: A Meta‐Analysis

Bruton's tyrosine kinase inhibitors (BTKis) have revolutionized the treatment of chronic lymphocytic leukemia (CLL), with significantly improved outcomes for both treatment-naïve (TN) and relapsed/refractory (R/R) patients. BTKis bind irreversibly to the cysteine 481 (C481) residue of the BTK molecule inhibiting B-cell receptor (BCR)-mediated intracellular signals crucial for CLL-cell survival [1]. Despite its efficacy, long-term BTKi therapy often leads to therapy resistance with subsequent disease progression (DP) [2]. Resistance mechanisms predominantly relate to mutations in BTK gene, particularly the mutation at C481S, which disrupts covalent BTKi binding. Additionally, mutations in phospholipase Cγ2 (PLCG2), which encodes for a downstream effector of BCR signaling, are emerging as significant additional contributors to resistance [3].

To comprehensively assess the prevalence and significance of these resistance mechanisms, we conducted a systematic review and meta-analysis to quantify the prevalence of BTK and PLCG2 mutations in CLL patients who experience DP while treated with BTKis. We performed a comprehensive search of the PubMed database and manually reviewed abstracts from major hematology conferences (American Society Hematology [ASH] and European Hematology Association [EHA]) to identify relevant studies. The analysis adhered to Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines to ensure methodological rigor and transparency [4].

Studies were included if they reported upon CLL patients treated with covalent BTKis and reported assessments for BTK and/or PLCG2 mutations at DP. Two reviewers (SM and DG) independently performed data extraction, with discrepancies resolved by consensus. The primary outcome was the pooled prevalence of BTK and PLCG2 mutations amongst patients with DP while treated with BTKis. A separate analysis compared patients treated with first-generation BTKi (ibrutinib) versus second-generation BTKis (acalabrutinib, zanubrutinib). Cross study heterogeneity was assessed using the chi-squared (χ2) Q test and the I2 statistic, with an I2 value greater than 50% indicating substantial heterogeneity.

Seventeen studies with 724 patients provided data on BTK somatic mutations [2, 3] (Figure S1; Table S1; Supporting Information: References [1–11]). These studies included six post hoc analyses of Phase 3 clinical trials (ALPINE, ELEVATE R/R, RESONATE, RESONATE-2, ILLUMINATE, FLAIR), five Phase 2 trials (PCYC-1122, RESONATE-17, NCT02337829, NCT01500733, NCT03740529 [BRUIN]), and three retrospective multicenter analyses (French Innovative Leukemia Organization [FILO], European Research Initiative on CLL [ERIC], Hungarian Ibrutinib Resistance Analysis Initiative). Additionally, three retrospective monocentric studies from the MD Anderson Cancer Center (MDACC), Peter MacCallum Cancer Centre, and The Ohio State University (OSU) Comprehensive Cancer Center were included [2, 3] (Supporting Information: References [1–11]). The majority of patients (86.4%) received ibrutinib-based therapies (ibrutinib monotherapy, 78%; ibrutinib combined with rituximab [IR], 8.4%), while a smaller subset (13.5%) received second-generation BTKis (acalabrutinib, 8.4%; zanubrutinib, 5.1%).

Overall, 7.8% of patients discontinued BTKi therapy due to adverse events (AEs) or other reasons. Of those who discontinued due to DP (n = 667), 86.3% had R/R CLL, and 13.6% had TN CLL. The meta-analysis demonstrated that, amongst patients with progressive CLL, pooled prevalence of BTK mutations was 52% (95% CI: 39%–64%), but with substantial heterogeneity across studies (Q = 161.54, p < 0.001, I2 = 91%) (Figure 1A).

Details are in the caption following the image
FIGURE 1
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Meta-analysis on the prevalence of Bruton tyrosine kinase (BTK) (A) and phospholipase Cγ2 (PLCG2) (B) somatic mutations amongst patients with disease progression (DP) while treated with BTK inhibitor therapy.

Fourteen studies, which encompassed 620 patients, were analyzed for PLCG2 mutations [2, 3] (Figure S2; Table S1) (Supporting Information: References [1–5, 9–11]). These cohorts were the same as those analyzed for BTK mutations, except for the noninclusion of the patients from the MDACC, Peter MacCallum Cancer Centre, and the Hungarian Ibrutinib Resistance Analysis Initiative, which did not provide data on PLCG2 mutations. Most patients in the PLCG2 cohort were treated with ibrutinib-based therapies (ibrutinib-monotherapy, 80.3%; IR, 9.8%), while a smaller proportion (13.7%) received second-generation BTKis (acalabrutinib, 9.8%; zanubrutinib, 3.8%). Discontinuation of BTKi therapy due to AEs or other reasons was observed in 9.2% of patients. Amongst patients with progressive CLL (n = 563), 86% had R/R CLL, and 14% had TN CLL. The pooled prevalence of PLCG2 mutations was 11% (95% CI: 7%–17%), with notable heterogeneity across studies (Q = 40.77, p < 0.001, I2 = 73%) (Figure 1B).

We further explored whether the prevalence of BTK or PLCG2 mutations differed between patients treated with the first-generation BTKi ibrutinib and those treated with the second-generation inhibitors acalabrutinib or zanubrutinib. The prevalence of BTK mutations was 56% (95% CI: 38%–74%) amongst ibrutinib-treated patients and 51% (95% CI: 26%–77%) amongst those treated with acalabrutinib or zanubrutinib (Figure S3). PLCG2 mutations were detected in 13% (95% CI: 6%–23%) of ibrutinib-treated patients, compared with 9% (95% CI: 0%–25%) in patients exposed to acalabrutinib or zanubrutinib (Figure S4).

Finally, we investigated whether pre-existing TP53 mutations (median 49.5%; range 22.9%–100%) or the duration of BTKi therapy (median 40.5 months; range 27.7–78 months) correlated with the development of BTK and PLCG2 mutations.

A positive correlation was found between the presence of PLCG2 mutations and the TP53 mutational burden (r2 = 0.872, p = 0.001), as well as the duration of BTKi therapy (r2 = 0.539, p = 0.02) (Figures S5 and S6). However, no significant correlation was observed between these factors and the presence of BTK mutations.

Our meta-analysis demonstrates that resistance to BTKis in CLL is multifaceted, with BTK mutations prevalent in over half of patients who experience DP. While PLCG2 mutations are less common, their association with a high TP53 mutation burden and prolonged BTKi exposure underscores their emergent role in secondary resistance mechanisms. These results may suggest that fixed-duration therapies could mitigate these resistance pathways, with potential improvement in long-term outcomes for patients [5, 6].

Given the limited representation of TN CLL patients in our dataset, these findings primarily pertain to patients with R/R CLL. Notably, most R/R patients were likely exposed to prior chemotherapy. In our aggregate analysis, however, we could not differentiate between R/R patients with and without prior chemotherapy exposure. Therefore, the specific contribution of prior chemotherapy to BTKi resistance mediated by BTK or PLCG2 mutations could not be assessed in detail.

Much of our knowledge in relation to the prevalence of BTK or PLCG2 mutations is derived from studies of ibrutinib-treated patients [2, 3] (Supporting Information: References [1–11]). A recent post hoc analysis of the ELEVATE-R/R trial, which compared acalabrutinib with ibrutinib in R/R high-risk CLL patients, revealed that the rate of emergent BTK mutations at relapse was significantly lower in those treated with ibrutinib as compared to acalabrutinib (37% vs. 69%) (Supporting Information: Reference [2]). However, due to the limited sample size associated with this analysis, the clinical significance of these findings remains uncertain. Additionally, the presence of higher risk genomic features amongst patients in the ELEVATE-RR trial, which contributes to genetic instability, limits the generalizability of these results (Supporting Information: Reference [2]). In our meta-analysis of trials involving ibrutinib and second-generation BTKis, we observed similar rates of BTK and PLCG2 mutations amongst patients with progressive disease, regardless of the specific BTKi used.

An important consideration in the transition from ibrutinib to second-generation BTKis is the emergence of additional BTK mutations that mediate resistance. In a post hoc analysis of the ELEVATE-R/R trial, T474I gatekeeper mutations were observed in 29% of patients exhibiting resistance to acalabrutinib (Supporting Information: Reference [2]). In a separate study examining patients treated with zanubrutinib, L528W mutations, known to impair kinase function, were detected at rates comparable to those of the C481S mutation (Supporting Information: Reference [3]). Our analysis confirms that the canonical C481S mutation remains the predominant mutation, accounting for approximately 60%–100% of BTK mutations in patients treated with ibrutinib or second-generation BTK inhibitors (Table S2).

Finally, it is important to acknowledge the limitations of our current meta-analysis. While our current study points to somatic genetic mutations as the primary drivers of resistance, one-third of the patients in our analysis lacked either detectable BTK or PLCG2 mutations. In these patients, resistance to BTKis may develop through nongenetic adaptive mechanisms that activate compensatory pro-survival pathways. Specifically, the activation of PI3K/AKT/ mTOR, NF-κB, and MAPK pathways, along with the upregulation of BCL2, MYC, and XPO1 or downregulation of PTEN, may enable B cell survival even in the presence of BTK inhibition [7]. Additionally, resistance may be further supported by microenvironmental factors, including chemokine and integrin signaling via upregulation of CXCR4 and VLA4 [7]. Such mechanisms may also be pathogenic mediators of BTKi therapy resistance, concepts, which challenge the predominant focus on genetic factors in this field of study.

Other limitations of this study include the inconsistent reporting of variant allele frequencies (VAFs), the reliance on peripheral blood samples that may not capture clonal evolution in lymph nodes and the lack of longitudinal data mapping mutation dynamics over time [8].

In summary, this meta-analysis provides a comprehensive insight into the prevalence of BTK and PLCG2 somatic mutations in CLL, which has lost sensitivity to BTKi therapy. Our report may lead to a further appreciation of genetic mechanisms of resistance to BTKis in CLL treatment. Ultimately, the heterogeneity of resistance mechanisms necessitate further research also into nongenetic factors driving DP.

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来源期刊
CiteScore
15.70
自引率
3.90%
发文量
363
审稿时长
3-6 weeks
期刊介绍: The American Journal of Hematology offers extensive coverage of experimental and clinical aspects of blood diseases in humans and animal models. The journal publishes original contributions in both non-malignant and malignant hematological diseases, encompassing clinical and basic studies in areas such as hemostasis, thrombosis, immunology, blood banking, and stem cell biology. Clinical translational reports highlighting innovative therapeutic approaches for the diagnosis and treatment of hematological diseases are actively encouraged.The American Journal of Hematology features regular original laboratory and clinical research articles, brief research reports, critical reviews, images in hematology, as well as letters and correspondence.
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